The present invention relates to a zoom lens of a camera, and more particularly to a zoom lens barrel assembly of a camera.
A telescoping type of zoom lens having a plurality of concentrically arranged moving barrels is Well known. This type of zoom lens is widely utilized in a camera for reducing the thickness of the camera when it is not in use. The conventional zoom lens is formed of a fixed barrel, an outer barrel fitted into the fixed barrel and a plurality of moving barrels. The outer barrel is provided on the inner peripheral surface thereof with a plurality of cam grooves for receiving therein a plurality of cam follower pins. Various moving barrels are fitted into the outer barrel for housing a first group of lenses and a second group of lenses. When the outer barrel is driven to move and rotate relative to the fixed barrel, the outer barrel can carry the moving barrels to move along the direction of the optical axis. Thereby, the optical system of the camera is formed.
The driving system for controlling the movements of the barrels is different from that for controlling the motions of the shutter. For example, the shutter, which is mounted in one of the moving barrels, is driven by a step motor. When the first group and the second group of lenses are moved to respective positions corresponding to a set focal length by the moving barrels, the shutter is driven by the step motor for taking a photograph, which is well known to one skilled in the art.
Please refer to FIG. 1, which is a longitudinal section view of the conventional zoom lens barrel. As shown in FIG. 1, a middle barrel 104 is fitted into the outer barrel 103 to relatively move. A guide ring 105 is mounted on the front end of the middle barrel 104 for guiding the linear moving barrel 102 to move along the direction of the optical axis. Three cam follower pins 107 are respectively mounted in the penetrated holes 1051 of the guide ring 105 to be served as supporters in the conventional method for keeping the moving range of the optical system. Recently, the camera has a design tendency of long focal length and wide moving range of the zoom lens barrels. However, when the rotating angle of the outer barrel is too small, the guide grooves formed on the inner periphery of the outer barrel 103 must be designed to have cliffy oblique angle. In this situation, the torque for rotating the outer barrel 103 will go beyond the requirement. Therefore, the conventional zoom lens barrel structure is unstable.
Certainly, in order to increase the moving range of the optical system and allow the cam follower pins 107 to rotate at a total rotating angle larger than 120, the gradient of the guide grooves of the outer barrel 103 is released. However, keeping the moving range of the cam follower pins 107 along the direction of optical axis would lead to the assembly of the guiding ring 105 and the middle barrel 104 hard. Recently, in order to solve the above-mentioned problems and allow the middle barrel 104 to rotate at a rotating angle larger than 120, the guide ring 105 is provided with a hook structure 1052 as shown in FIG. 2. However, in order to avoid the disengagement of the guide ring 105 and the middle barrel 104, the guide ring 105 must employ at least three hooks to hook the front end of the middle barrel 104. However, the hooks will deform and the guide ring 105 will disengage from the linear moving barrel 104 when a powerful external force is exerted upon the guide ring 105.
In addition, when the hooks are respectively forced to engage with the middle barrel 104, those parts will result in deformation due to the powerful external force. Therefore, it is required to reserve a buffer space. However, such design will result in the existence of the.clearance between those parts and derivate native influences on the optical system of a camera.
Therefore, it is desired for the applicant to develop a suitable zoom lens barrel assembly, which allows the middle barrel 104 thereof to move linearly and rotate in a rotating angle larger than 120, allows the guide ring 105 thereof to move with the middle barrel 104 along the direction of optical axis, and employs a plurality of cam follower pins 101 to guide the middle barrel 104 to move along the direction of optical axis. And, the cam follower pins can be respectively assembled with the guide ring 105 and middle barrel 104 simply and correctly without exerting a powerful external force upon the cam follower pins 101.
It is therefore an object of the present invention to provide a zoom lens barrel assembly which allows the middle barrel thereof to move linearly and rotate in a rotating angle larger than 120, allows the guide ring thereof to move with the middle barrel along the direction of optical axis, and employs a plurality of cam follower pins to guide the middle barrel to move along the direction of optical axis.
To achieve the object of the present invention, a zoom lens barrel is provided. The zoom lens barrel includes a moving barrel provided on the outer peripheral surface of the front portion thereof with a flange and a circumferential groove adjacent to the flange, a guide ring having at least one penetrated hole on the outer peripheral surface thereof and a slider way therein, and at least one cam follower pin having one end piercing through the penetrated hole of the guide ring and disposed in the circumferential groove of the moving barrel. The flange of the moving barrel is received in the slider way of the guide ring and limited by the end of the cam follower pin, thereby the guide ring is rotatably mounted on the front portion of the moving barrel.
Preferably, the cam follower pin has a semicircle-shaped projection and a flat surface on the end. More preferably, the other end of the cam follower pin has a taper portion.
There is further an object of the present invention to provide a zoom lens barrel assembly. The zoom lens barrel assembly includes: an outer barrel provided on the inner peripheral surface thereof with at least one key guide groove and at least one cam groove; a middle barrel fitted into the outer barrel and provided on the outer peripheral surface of the front portion thereof with at least one guide key, a flange and a circumferential groove adjacent to the flange, wherein the guide key is positioned in the key guide groove of the outer barrel; a middle guide ring rotatably mounted on the front end of the middle barrel, and having at least one penetrated hole on the outer periphery thereof and a slider way therein; at least one cam follower pin, one end of which is piercing through the penetrated hole of the guide ring and disposed in the circumferential groove of the middle barrel and the other end of which is movable disposed in the cam groove of the outer barrel; and an inner barrel fitted into the middle barrel.
In accordance with one aspect of the present invention, the zoom lens barrel assembly further includes a fixed barrel provided on the inner peripheral surface thereof with female helicoids which are engaged by male helicoids formed on the outer peripheral surface of the outer barrel.
Preferably, the key guide groove is extending parallel to the direction of optical axis and the cam groove is formed oblique to the optical axis.
Preferably, the guide key of the middle barrel is projecting outwardly from the middle barrel in a radial direction.
In accordance with another aspect of the present invention, the flange of the middle barrel is provided on the outer peripheral surface of the front end of the middle barrel.
In accordance with another aspect of the present invention, the zoom lens barrel assembly further includes a first guide plate secured to the middle guide ring by screws.
In accordance with another aspect of the present invention, the first guide plate has a plurality of L-shaped guide projections respectively inserted into the rectangle guide channels formed on the middle guide ring.
In accordance with another aspect of the present invention, each of the L-shaped guide projection is extending parallel to the optical axis.
In accordance with another aspect of the present invention, the zoom lens barrel assembly further includes a second guide plate provided on the rim thereof with a plurality of guide projections, wherein each of the guide projections is respectively extending downwardly from the rim thereof
In accordance with another aspect of the present invention, portions of the guide projections are slidably mounted in the key guide channel formed on the inner peripheral surface of the fixed barrel, and the other portion of the projections are respectively inserted into the corresponding rectangle guide channels formed on the middle guide ring to prevent the middle guide ring from rotating relative to the fixed barrel.
In accordance with another aspect of the present invention, the zoom lens barrel assembly further includes an outer barrel guide ring secured to the second guide plate by screws.
In accordance with another aspect of the present invention, the clearance formed between the outer barrel guide ring and the second guide plate is employed to clip the inner extending ring formed on the outer barrel.
In accordance with another aspect of the present invention, the inner barrel is provided on the outer peripheral surface thereof with male helicoids which are engaged by female helicoids formed on the inner peripheral surface of the middle barrel.
In accordance with another aspect of the present invention, the zoom lens barrel further includes a linear barrel fitted into the inner barrel.
In accordance with another aspect of the present invention, the inner barrel is provided on the inner peripheral surface thereof with at least one linear strip which is engaged by at least one key guide channel formed on the outer peripheral surface of the linear barrel.
In accordance with another aspect of the present invention, the zoom lens barrel further includes a spring disposed between the linear barrel and the inner barrel.
In accordance with another aspect of the present invention, the cam follower pin has a semicircle-shaped projection and a flat surface on the end.